Device and method for detecting force factor of loudspeaker

Abstract

A method and device for detecting a force factor of a loudspeaker is provided. The method includes the steps of: providing the loudspeaker with a dynamic driving voltage signal; continuously measuring a current signal flowing through the loudspeaker; observing the current signal and if the current signal shows that the diaphragm excursion of the loudspeaker is greater than an displacement limit, decreasing the driving voltage signal until the current signal shows that the diaphragm excursion of the loudspeaker is less than or equal to the displacement limit; and substituting the current driving voltage signal, the current signal, the displacement limit, and an electrical impedance of the loudspeaker into a function so as to compute the force factor of the loudspeaker.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This non-provisional application claims priority claim under 35 U.S.C. §119(a) on Taiwan Patent Application No. 103102385 filed Jan. 23, 2014, the entire contents of which are hereby incorporated by reference.BACKGROUND[0002]1. Field of the Invention[0003]The present invention relates to a device and method for detecting a force factor of a loudspeaker and, more particularly, to a device and method that are utilized by end users so as to accurately detect the force factor of a loudspeaker.[0004]2. Description of Related Art[0005]To protect the physical structure of a loudspeaker from being permanently damaged, it is a practice not to directly drive a loudspeaker with a linearly-amplified audio signal, which may, if the driving signal is too large, cause greater diaphragm excursion or even exceed beyond the displacement limit of the diaphragm excursion, thus leading to a change in the property, or a shorter lifetime, of the diaphragm of th...

AI Technical Summary

Benefits of technology

The present invention provides a method to accurately detect the force factor of a loudspeaker during normal operation. This method can be used by end users or applied during production testing, making it more useful and convenient.

Problems solved by technology

To protect the physical structure of a loudspeaker from being permanently damaged, it is a practice not to directly drive a loudspeaker with a linearly-amplified audio signal, which may, if the driving signal is too large, cause greater diaphragm excursion or even exceed beyond the displacement limit of the diaphragm excursion, thus leading to a change in the property, or a shorter lifetime, of the diaphragm of the loudspeaker, or even direct damage to the structure of the diaphragm.

Therefore, it has become an issue of the design of a loudspeaker and its driving circuit on how to detect, or predict, the diaphragm excursion so as to make an optimal tradeoff between the output volume and the protection of the loudspeaker.

Therefore, with the known driving voltage u, one can obtain the magnitude of the BEMF Φ*v by measuring the current i. However, the diaphragm excursion (i.e., the integral of the velocity of displacement v) cannot be obtained without first computing the magnitude of the force factor Φ.

Besides, the measurement of the SPL requires some special instruments, which may not be easily accessible to the end users.

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